Microbial Diseases of the Upper Respiratory System Most common type of infection and can infect other parts of body Consists of nose, pharynx, associated structures (middle ear, auditory tubes) Coarse hairs in nose filter large particles; ciliated mucous membranes of nose and throat trap airborne particles and remove them Specific areas become infected (self-limiting/healing) to produce: Lymphoid tissue, tonsils, and adenoids provide immunity to certain infections Laryngitis: S. pneumoniae, S. pyogenes, viruses Tonsillitis: S. pneumoniae, S. pyogenes, viruses Sinusitis: Bacteria Epiglottitis: H. influenzae Characterize the normal microbiota of the upper and lower respiratory systems. Describe how microorganisms are prevented from entering the respiratory system.
Upper respiratory normal microbiota may include pathogens Upper Respiratory System Figure 24.1
Lower Respiratory System Consists of larynx, trachea, bronchial tubes, and alveoli Ciliary escalator helps prevent microorganisms from reaching lungs Microbes in lungs phagocytized by alveolar macrophages Respiratory mucus contains IgA antibodies Lower respiratory system usually sterile due to ciliary escalator
Lower Respiratory System Consists of larynx, trachea, bronchial tubes, and alveoli.
Streptococcal pharyngitis (Strep throat) Figure 24.3 Streptococcus pyogenes (group A beta-hemolytic) Inflammation of mucous membrane and fever, tonsillitis and otitis media Diagnosis by indirect agglutination Resistant to phagocytosis Penicillin treatment Streptokinases lyse clots Streptolysins are cytotoxic Differentiate among pharyngitis, laryngitis, tonsillitis, sinusitis, and epiglottitis. Simply dependent upon which structure is attacked by bacteria.
Streptococcus pyogenes – strep throat can result in scarlet fever Red rash, high fever, strawberry tongue Pharyngitis also Erythrogenic toxin produced by lysogenized S. pyogenes Scarlet Fever – strawberry tongue Figure 24.4
Corynebacterium diphtheriae: Gram-positive rod Diphtheria membrane of fibrin, dead tissue, and bacteria forms in throat, sometimes blocking air Diphtheria exotoxin produced by lysogenized C. diphtheriae – inhibits protein synthesis, heart/kidney/nerve damage can result Antitoxin necessary to neutralize toxin; antibiotics too Prevented by DTaP and Td vaccine (Diphtheria toxoid) Cutaneous diphtheria - Infected skin wound leads to slow healing ulcer Diphtheria List the causative agent, symptoms, prevention, preferred treatment, and laboratory identification tests for streptococcal pharyngitis, scarlet fever, diphtheria, cutaneous diphtheria, and otitis media.
Otitis Media - earache Often a complication of nose and throat infections Pus accumulation can cause pressure on eardrum Streptococcus pneumoniae (35%) Haemophilus influenzae (20-30%) Moraxella catarrhalis (10-15%) Streptococcus pyogenes (8-10%) Staphylococcus aureus (1-2%) Treated with broad-spectrum antibiotics Incidence of S. pneumoniae reduced by vaccine
Acute Otitis Media – bulging eardrum Figure 25.7
Can be caused by nearly 200 different viruses Rhinoviruses (50%) – grow best slightly below body temperature Coronaviruses (15-20%) Rhinoviruses attached to ICAN-1 on nasal mucosa Antibodies produced against specific viruses Complications can include infections in sinuses, larynx, ear, lower respiratory Most often transmitted by indirect contact, therefore more colds in cold weather due to greater indoor contact and physiological changes Common cold List the causative agents and treatments for the common cold.
Similar organisms attack both upper and lower respiratory systems Bacteria, viruses, & fungi cause: Bronchitis Bronchiolitis Pneumonia Microbial Diseases of the Lower Respiratory System
Lower Respiratory System The ciliary escalator keeps the lower respiratory system sterile. Figure 24.2
Stage 1: Catarrhal stage, like common cold Stage 2: Paroxysmal stage: Violent coughing sieges due to accumulation of mucus in trachea and bronchi Stage 3: Convalescence stage can last for months Lab diagnosis based on isolation and selective media, followed by serological tests Regular immunization has decreased incidence Pertussis (Whooping Cough) List the causative agent, symptoms, prevention, preferred treatment, and laboratory identification tests for pertussis and tuberculosis.
Tuberculosis Figure 24.9 Mycobacterium tuberculosis: Acid-fast rod. Transmitted from human to human Lipids in cell wall are acid- fast and resistant to drying and disinfectants M. bovis: <1% U.S. cases, not transmitted from human to human (unpasteurized milk) M. avium-intracellulare complex infects people with late stage HIV infection
“Military” tuberculosis develops when caseous lesion ruptures and releases bacteria into blood or lymph vessels Characterized by weight loss, coughing, low vigor Treatment of Tuberculosis: Prolonged treatment with multiple antibiotics – two drugs taken for 1-2 years due to multidrug-resistant M. tuberculosis Vaccines: BCG - live, avirulent M. bovis. Not widely used in U.S. Tuberculosis
Figure 24.11 Diagnosis: Tuberculin skin test screening + = current or previous infection Followed by X-ray or CT, acid-fast staining of sputum, culturing bacteria (up to 8 weeks incubation)
Pneumomoccal Pneumonia Figure 24.13 Streptococcus pneumoniae: Gram- positive encapsulated diplococci Fever, breathing difficulty, chest pain, rust-colored sputum Most common cause of pneumococcal pneumonia Diagnosis by culturing bacteria Penicillin is drug of choice Compare and contrast the seven bacterial pneumonias discussed in this chapter.
Pneumomoccal Pneumonia Bacterial isolation, then sensitivity testing to various antibiotics for treatment choice
Gram-negative coccobacillus Alcoholism, poor nutrition, cancer, or diabetes are predisposing factors Second-generation cephalosporins for treatment Haemophilus influenzae Pneumonia
Mycoplasmal Pneumonia – endemic disease Figure 24.14 Mycoplasma pneumoniae: pleomorphic, wall- less bacteria Also called primary atypical pneumonia and walking pneumonia Common in children and young adults Diagnosis by PCR or by IgM antibodies
Mycoplasmal Pneumonia Figure 11.19a, b Arrowheads indicate terminal structures that probably aid in attachment to eukaryotic cells (left); filamentous growth (right)
Legionella pneumophila: Gram-negative rod L. pneumophila is found in water (air-conditioning units) Transmitted by inhaling aerosols, not transmitted from human to human Diagnosis: culturing bacteria and DNA probes Treatment: Erythromycin Legionellosis
Chlamydia psittaci: gram-negative intracellular bacterium Transmitted by elementary bodies (allow bacteria to survive outside host) from bird dropping to humans Reorganizes into reticulate body after being phagocytized Diagnosis: culturing bacteria in eggs or cell culture Treatment: Tetracycline Psittacosis (Ornithosis)
Chlamydia pneumoniae Transmitted from human to human Diagnosis by FA (fluorescent antibody) test Treatment: Tetracycline Chlamydial Pneumonia
Q fever Mycoplasma pneumoniae: obligately parasitic, intracellular, pleomorphic, wall-less bacteria Transmitted to humans from unpasteurized milk or inhalation of dairy barn aerosols Inhaling a single pathogen is enough to cause infection Diagnosis by isolation and growth in eggs or cell cultures, serological tests
Q fever Figure 24.15 List the causative agent, symptoms, prevention, and preferred treatment for viral pneumonia, RSV, and influenza.
Viral pneumonia as a complication of influenza, measles, chickenpox Viral etiology suspected if no cause determined Respiratory Syncytial Virus (RSV) Common in infants; 4500 deaths annually Causes cell fusion (syncytium) in cell culture Symptoms: coughing Diagnosis by serologic test for viruses and antibodies Treatment: Ribavirin Viral Pneumonia
Chills, fever, headache, muscle aches (no intestinal symptoms) Viral strains identified by antigenic differences in the H and N spikes that project from outer lipid bilayer of virus Hemagglutinin (H) spikes used for attachment to host cells Neuraminidase (N) spikes used to release virus from cell Antigenic shifts make natural immunity and vaccination ineffective 1% mortality due to secondary bacterial infections Treatment: Amantadine and rimantadine Vaccine for high-risk individuals Influenza
Figure 24.16 Protein layer (capsid) covered by lipid bilayer (envelope) and two types of spikes Genome of 8 segments of RNA
Antigenic shift Changes in H and N spikes Probably due to genetic recombination between different strains infecting the same cell Antigenic drift Mutations in genes encoding H or N spikes May involve only 1 amino acid Allows virus to avoid mucosal IgA antibodies Influenza
A: causes most epidemics, H 3 N 2, H 1 N 1, H 2 N 2 B: moderate, local outbreaks C: mild disease Influenza serotypes
Histoplasmosis Figure 24.17 Fungal diseases increasing in recent years Histoplasma capsulatum, dimorphic fungus Droppings of birds and bats (airborne conidia) (a) 37˚(b) <35˚ Filamentous spore-forming phase List the causative agent, mode of transmission, preferred treatment, and laboratory identification tests for four fungal diseases of the respiratory system.
Histoplasmosis Figure 24.18 Transmitted by airborne conidia from soil Diagnosis by culturing fungus Treatment: amphotericin B
Coccidioidomycosis Figure 24.20 Transmitted by airborne arthrospores Diagnosis by serological tests or DNA probe Treatment: amphotericin B
Pneumocystis Pneumonia Figure 24.22 Pneumocystis jiroveci (formerly P. carinii) found in healthy human lungs Pneumonia occurs in newly infected infants & immunosuppressed individuals Treatment: Timethoprim- sulfamethoxazole Cyst stage in alveolus of monkey lung
Pneumocystis jiroveci (pneumonia) Figure 24.21 The mature cyst contains 8 intracystic bodies. The cyst ruptures, releasing the bodies. The bodies develop into trophozoites. 1 2 3 The trophozoites divide. 4 Each trophozoite develops into a mature cyst. 5 Cyst Intracystic bodies Trophozoite
Blastomyces dermatitidis, dimorphic fungus Found in soil Can cause extensive tissue destruction (abscesses) Treatment: amphotericin B Blastomycosis